Preparation of lead-sodiummagnesium alloys



Patented Nov. 17, 193% UNITED STATES- [PATENT OFFICE PREPARATION orLEAD-SODIUM- ,MAGNESIUM .ALLoYs No Drawing.

Application November 16, 1934, Serial No. 753,301

4 Claims. (01. 15-161) This invention relates to the preparation oflead-sodium-magnesium alloys.

An alloy comprising 10% sodium, 89.95% to 89.00% lead and 0.05 to 1.00%magnesium is de- 5-v scribed in an application of F. B. Downing and L.S. Bake, Ser. No. 708,248 filed January 25, 1934. A process employingthis alloy is described and claimed in an application of Downing andBake, Ser. No. 613,260, filed May 24,

10 1932. .These applications of Downing and Bake 20 in discharging thestill. If magnesium is present,

the'residual lead, after the distillation, tends to be finely dividedandls easily discharged.

There are two general methods of preparing the ordinary lead-monosodiumalloy. The first 25 method consists in placing the required amount oflead and sodium in a pot and applying heat thereto until the reactiontakes place to form PbNa. The reaction of lead and sodium to form thelead-sodium alloy is exothermic. when this method is practiced, enoughheat is liberated to raise the temperature of the alloy to from 500 to670 C. At these high temperatures, there is a very strong tendency forthe sodium to distill ofl and, if great care is not taken, the resulting35 alloy will contain less than 10% sodium. This is a decidedlyundesirable result as, if the amount of sodium varies as much as 0.1 to0.2% below or above 10% the alloy will not produce the maximum yields oftetraethyl lead. Magnesium 40 has a melting point of about 651 C.Accords 'ingly, magnesium may be dissolved in the alloy by this methodas the magnesium is soluble in the lead 'sodium' alloy at such hightemperatures. However, such method involves the prob- 45 ileum ofavoiding distillation of sodium from the 0y. I y

The second method of preparing lead-monosodium alloy, and the methodwhich is more generally employed at the present time, consists 50 eitherin adding molten sodium to molten lead or molten lead to molten sodiumat the desired rate with stirring in a pot jacketed with moltendipheny'l.- In.. this process, the rate of ,addition of one ingredientto the other may be so con- 55 trolled that the temperature within thepot does.

not exceed 400 C. At this temperature, there is little tendency for thesodium to distill ed. and, furthermore, such temperatures are necessaryto prevent decomposition of the diphenyl. Diphenyl starts to decomposeat about 400 C. but such decomposition does not becomeserious untiltemperatures of about 410 C. and above are reached. However, at thetemperature of about 400 C., it was found that, when magnesium was addedto the alloy, it did not go into solution in the alloy but remainedfloating on the surface of the molten alloy.

An object of the present invention is to provide a method for preparinglead-sodium-magnesium alloys such as are disclosed in the hereinbeioreidentified applications of Downing and Bake. A further object is toprovide a'method whereby such an alloy can-be prepared at temperaturesnot in excess of 400 6. Other objects are to advance the art. Stillother objects ,will appear hereinafter.

These objects "may be accomplished in accordance with our inventionwhich comprises fusing the magnesium with at least a major proportion ofthe lead to produce a le'ad-magnesium alloy which may be melted andadded to the molten sodium or to which molten sodium may be added.

Our invention is based upon the discovery that lead-magnesium alloysdecrease in their melting points with increasing amounts of magnesiumuntil a minimum melting point of approximately 250 C. is reached, whenthe alloy contains about 3% of magnesium. When the percent of magnesiumis increased above this point, the melting point gradually rises to551.3 C. at 19.06% magnesium at which point only PbMgz is present. Themelting point then decreases to 468 C. at approximately 35% magnesiumand then increases gradually to 651 C.,

when pure magnesium is present. On the way up from the minimum of 250(3., the melting point curve crosses the 400 C. line at approximately8.7% magnesium. Accordingly, it is evi-= dent that, if any leadmagnesium alloy containing up to 8.7% of magnesium is added to amoitenlead-sodium alloy at 400 0., fusion of the lead magnesium alloy will beefiected and a. homogeneous mixture of the magnesium will be obtained. 7

We have found that lead-magnesium alloys having a melting point up toabout 500 C. may be melted andthen added to molten sodium or a moltenlead-sodium alloy and such leadmagnesium alloy will dissolve in thesodium. e

lead-sodium alloy and form a homogeneous mixture therewith. According tothe broader ashave melting points below 500 C. and fall within thebroader aspects of our invention. However, it will generally bedesirable to use leadmagnesium alloys containing not more than 8.7%

' of magnesium as these alloys will melt at temsium and 89.95% lead.

peratures not higher than about 400 C. and

hence are more convenient to employ. Furthermore, magnesium,up' toapproximately is very soluble in lead at the molten temperature of 327C. Therefore, a homogeneous mixture of magnesium in the desired amountof lead-sodium alloy can be obtained by first dissolving the requiredamount ofmagnesium in the molten lead before adding to thesodium orbefore adding the'sodium to the molten lead-magnesium alloy. Thislatterfmethod appears to be the simplest and most practical and is thepreferred method of practicing our invention;

In order to more clearly illustrate our invention and the preferredmodes of carrying the same into efiect, the following examples aregiven:

' Example 1 1000 lbs. of molten sodium were gradually Example 2 The sameprocess employed in Example 1 was followed except that only 7000 lbs. oflead were employedand 2000 lbs. of the lead-magnesium alloy was addedthereto. The resulting product contained sodium, 89% lead and l%magnesium. r-

Example 3 1000 lbs. of molten sodium was added to 8985.7 lbs. of moltenlead at 400 C; The resulting leadsodium alloy was maintained at 400 C.while 14.3 lbs. of a lead-magnesium alloy containing magnesium was addedthereto. The resulting alloy contained 10% sodium, 0.05%

Example 4 'A mixture of 1000 lbs. of sodium and amis of lead wasprepared and maintained at a tem- 35% sodium, 1%

magnesium and 89% lead.

magneing' 10% of maghesiump- The product contained 10% Example 5 5 lbs.of magnesium were dissolved in 8995 lbs. of lead at 327 C. Themoltenlead-magnesium alloy was then added to 1000 lbs. of molten sodiumwith stirring- The resulting product-contained 10% 89.95% lead.

Example 6 100 lbs. of magnesium were dissolved in 8900 lbs. of lead at327- C. To this was added 1000 lbs. of molten sodium with stirring andwithout permitting the temperature to rise above 400 C. The resultingproduct contained 10% sodium, 1% magnesium, and 89% lead.

While we have disclosed the preferred embodiments of our invention, itwill be readily apparent to those skilled in the art that many variations and modifications may be made therein without. departing'fromthe spirit thereof. Ac-

cordingly, the scope 'of our invention is to be limited solely by theappended claims, construed as broadly as'is permissible in view art.

We claim: 1. The process of preparing an alloy comprising 10% sodium,89.95% to 89.00% lead and of the prior I sodium, 0.05% magnesium and0.05% to 1.00% magnesium which comprises fusing the magnesium withsuflicient molten lead to produce a mixture melting below 500 C. andthen fusing the mixture with 'suflicient sodium and lead to produce thealloy, the magnesium being fused with the lead at temperatures below themelting point of the magnesium and the lead-magnesium mixture beingfused with the sodium at temperatures below 500 C. and above the meltingpoint ofsaid mixture.

2. The process of-preparing an alloy comprising 10% sodium, 89.95% .to89.00% lead and 0.05% l to 1.00% magnesium which comprises fusing themagnesium with at least 90% of the *5 molten lead and then fusing themixture with suiiicient sodium and lead to produce the alloy,

the magnesium being fused with the lead at temperatures below themelting point of the magnesium and the lead-magnesium mixture beingfused with the sodium at temperatures below 500 C. and above the meltingpoint of said mixture.

3. The process of preparing an alloy comprising 10% sodium, 09.95% to89.00% lead and 0.05% to 1.00% magnesium which comprises fusing themagnesium with the molten lead and then fusing the mixture with thesodium, the magnesium being fused with the lead attemperatures below themelting point of the magnesium and the lead-magnesium mixture beingfused with the" sodium at temperatures below 500 C. and above themelting point of said mixture.

4. The method of preparing an alloy comprissodium, 89.95% to 89.00% leadand 0.05% to 1.00% magnesium which comprises fusing the magnesium withthe lead at about 327 C. and then adding the sodium while maintainin thetemperature to below about 400 C.

FREDERICK BAXTER DOWNING LOUIS SAMUELv BAKE. ALFRED PARLIELEE.

